tweaks for enabling unity builds

mostly changes to make sure anonymous namespaces don't clash and a change to avoid windows headers from leaking into other compilation units

unity builds are not yet enabled by default, but can be enabled by uncommenting this line in the root `xmake.lua`

```
--add_rules("c++.unity_build")
```

15 files changed, 72 insertions, 28 deletions

diff --git a/xmake.lua b/xmake.lua
index 7b5822371..1b6724044 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -32,6 +32,7 @@ if not is_arch("arm64") then
 end
 
 add_rules("mode.debug", "mode.release")
+--add_rules("c++.unity_build")
 
 if is_mode("release") then
     set_optimize("smallest")
diff --git a/zen/xmake.lua b/zen/xmake.lua
index 86d95406e..b83999efc 100644
--- a/zen/xmake.lua
+++ b/zen/xmake.lua
@@ -4,6 +4,7 @@ target("zen")
     set_kind("binary")
     add_headerfiles("**.h")
     add_files("**.cpp")
+    add_files("zen.cpp", {unity_ignored  = true })
     add_deps("zencore", "zenhttp", "zenutil")
     add_includedirs(".")
     set_symbols("debug")
diff --git a/zenhttp/httpserver.cpp b/zenhttp/httpserver.cpp
index 952857f2c..3576d9b3d 100644
--- a/zenhttp/httpserver.cpp
+++ b/zenhttp/httpserver.cpp
@@ -4,7 +4,6 @@
 
 #include "httpasio.h"
 #include "httpnull.h"
-#include "httpsys.h"
 
 #include <zencore/compactbinary.h>
 #include <zencore/compactbinarybuilder.h>
@@ -705,6 +704,9 @@ enum class HttpServerClass
 	kHttpNull
 };
 
+// Implemented in httpsys.cpp
+Ref<HttpServer> CreateHttpSysServer(int Concurrency, int BackgroundWorkerThreads);
+
 Ref<HttpServer>
 CreateHttpServer(std::string_view ServerClass)
 {
@@ -741,7 +743,7 @@ CreateHttpServer(std::string_view ServerClass)
 #if ZEN_WITH_HTTPSYS
 		case HttpServerClass::kHttpSys:
 			ZEN_INFO("using http.sys server implementation");
-			return new HttpSysServer(std::thread::hardware_concurrency(), /* background worker threads */ 16);
+			return CreateHttpSysServer(std::thread::hardware_concurrency(), /* background worker threads */ 16);
 #endif
 
 		case HttpServerClass::kHttpNull:
diff --git a/zenhttp/httpsys.cpp b/zenhttp/httpsys.cpp
index 4b566905e..16ec135cd 100644
--- a/zenhttp/httpsys.cpp
+++ b/zenhttp/httpsys.cpp
@@ -1662,5 +1662,11 @@ HttpSysServer::RegisterService(HttpService& Service)
 	RegisterService(Service.BaseUri(), Service);
 }
 
+Ref<HttpServer>
+CreateHttpSysServer(int Concurrency, int BackgroundWorkerThreads)
+{
+	return Ref<HttpServer>(new HttpSysServer(Concurrency, BackgroundWorkerThreads));
+}
+
 }  // namespace zen
 #endif
diff --git a/zenhttp/xmake.lua b/zenhttp/xmake.lua
index 528b72d52..b0dbdbc79 100644
--- a/zenhttp/xmake.lua
+++ b/zenhttp/xmake.lua
@@ -4,6 +4,7 @@ target('zenhttp')
     set_kind("static")
     add_headerfiles("**.h")
     add_files("**.cpp")
+    add_files("httpsys.cpp", {unity_ignored=true})
     add_includedirs("include", {public=true})
     add_deps("zencore")
     add_packages(
diff --git a/zenhttp/zenhttp.cpp b/zenhttp/zenhttp.cpp
index 0194abdcb..1adca30e8 100644
--- a/zenhttp/zenhttp.cpp
+++ b/zenhttp/zenhttp.cpp
@@ -2,6 +2,7 @@
 
 #include <zenhttp/zenhttp.h>
 
+#include <zenhttp/httpclient.h>
 #include <zenhttp/httpserver.h>
 #include <zenhttp/httpshared.h>
 
diff --git a/zenserver-test/xmake.lua b/zenserver-test/xmake.lua
index 57df8b356..f0b34f6ca 100644
--- a/zenserver-test/xmake.lua
+++ b/zenserver-test/xmake.lua
@@ -4,6 +4,7 @@ target("zenserver-test")
     set_kind("binary")
     add_headerfiles("**.h")
     add_files("*.cpp")
+    add_files("zenserver-test.cpp", {unity_ignored  = true })
     add_deps("zencore", "zenutil", "zenhttp")
     add_deps("zenserver", {inherit=false})
     add_packages("vcpkg::http-parser", "vcpkg::mimalloc")
diff --git a/zenserver/auth/authservice.cpp b/zenserver/auth/authservice.cpp
index 761c087f4..1cc679540 100644
--- a/zenserver/auth/authservice.cpp
+++ b/zenserver/auth/authservice.cpp
@@ -1,8 +1,9 @@
 // Copyright Epic Games, Inc. All Rights Reserved.
 
-#include <auth/authmgr.h>
 #include <auth/authservice.h>
 
+#include <auth/authmgr.h>
+
 #include <zencore/compactbinarybuilder.h>
 #include <zencore/string.h>
 
diff --git a/zenserver/diag/logging.cpp b/zenserver/diag/logging.cpp
index 1a8b427ca..ca569c467 100644
--- a/zenserver/diag/logging.cpp
+++ b/zenserver/diag/logging.cpp
@@ -326,7 +326,6 @@ private:
 	memory_buf_t		 m_CachedDatetime;
 	std::string			 m_LogId;
 };
-}  // namespace logging
 
 bool
 EnableVTMode()
@@ -355,6 +354,8 @@ EnableVTMode()
 	return true;
 }
 
+}  // namespace logging
+
 #if ZEN_USE_SENTRY
 
 class sentry_sink final : public spdlog::sinks::base_sink<spdlog::details::null_mutex>
@@ -391,8 +392,7 @@ void
 InitializeLogging(const ZenServerOptions& GlobalOptions)
 {
 	zen::logging::InitializeLogging();
-
-	EnableVTMode();
+	logging::EnableVTMode();
 
 	bool					  IsAsync  = true;
 	spdlog::level::level_enum LogLevel = spdlog::level::info;
diff --git a/zenserver/xmake.lua b/zenserver/xmake.lua
index 992923d48..23bfb9535 100644
--- a/zenserver/xmake.lua
+++ b/zenserver/xmake.lua
@@ -2,9 +2,10 @@
 
 target("zenserver")
     set_kind("binary")
+    add_deps("zencore", "zenhttp", "zenstore", "zenutil")
     add_headerfiles("**.h")
     add_files("**.cpp")
-    add_deps("zencore", "zenhttp", "zenstore", "zenutil")
+    add_files("zenserver.cpp", {unity_ignored  = true })
     add_includedirs(".")
     set_symbols("debug")
 
@@ -17,6 +18,7 @@ target("zenserver")
         add_ldflags("/MANIFEST:EMBED")
         add_ldflags("/LTCG")
         add_files("zenserver.rc")
+        add_cxxflags("/bigobj")
     else
         remove_files("windows/**")
     end
diff --git a/zenstore/blockstore.cpp b/zenstore/blockstore.cpp
index 5d81d1120..d743c431f 100644
--- a/zenstore/blockstore.cpp
+++ b/zenstore/blockstore.cpp
@@ -859,7 +859,7 @@ TEST_CASE("blockstore.blockfile")
 	CHECK(!std::filesystem::exists(RootDirectory / "1"));
 }
 
-namespace {
+namespace blockstore::impl {
 	BlockStoreLocation WriteStringAsChunk(BlockStore& Store, std::string_view String, size_t PayloadAlignment)
 	{
 		BlockStoreLocation Location;
@@ -907,10 +907,12 @@ namespace {
 
 		return IoBufferBuilder::MakeCloneFromMemory(Values.data(), Values.size());
 	}
-}  // namespace
+}  // namespace blockstore::impl
 
 TEST_CASE("blockstore.chunks")
 {
+	using namespace blockstore::impl;
+
 	ScopedTemporaryDirectory TempDir;
 	auto					 RootDirectory = TempDir.Path();
 
@@ -939,6 +941,8 @@ TEST_CASE("blockstore.chunks")
 
 TEST_CASE("blockstore.clean.stray.blocks")
 {
+	using namespace blockstore::impl;
+
 	ScopedTemporaryDirectory TempDir;
 	auto					 RootDirectory = TempDir.Path();
 
@@ -963,6 +967,8 @@ TEST_CASE("blockstore.clean.stray.blocks")
 
 TEST_CASE("blockstore.flush.forces.new.block")
 {
+	using namespace blockstore::impl;
+
 	ScopedTemporaryDirectory TempDir;
 	auto					 RootDirectory = TempDir.Path();
 
@@ -984,6 +990,8 @@ TEST_CASE("blockstore.flush.forces.new.block")
 
 TEST_CASE("blockstore.iterate.chunks")
 {
+	using namespace blockstore::impl;
+
 	ScopedTemporaryDirectory TempDir;
 	auto					 RootDirectory = TempDir.Path();
 
@@ -1078,6 +1086,8 @@ TEST_CASE("blockstore.iterate.chunks")
 
 TEST_CASE("blockstore.reclaim.space")
 {
+	using namespace blockstore::impl;
+
 	ScopedTemporaryDirectory TempDir;
 	auto					 RootDirectory = TempDir.Path();
 
@@ -1193,6 +1203,8 @@ TEST_CASE("blockstore.reclaim.space")
 
 TEST_CASE("blockstore.thread.read.write")
 {
+	using namespace blockstore::impl;
+
 	ScopedTemporaryDirectory TempDir;
 	auto					 RootDirectory = TempDir.Path();
 
diff --git a/zenstore/compactcas.cpp b/zenstore/compactcas.cpp
index 70a88ecad..60644847f 100644
--- a/zenstore/compactcas.cpp
+++ b/zenstore/compactcas.cpp
@@ -732,7 +732,7 @@ CasContainerStrategy::OpenContainer(bool IsNewStore)
 #if ZEN_WITH_TESTS
 
 namespace {
-	static IoBuffer CreateChunk(uint64_t Size)
+	static IoBuffer CreateRandomChunk(uint64_t Size)
 	{
 		static std::random_device rd;
 		static std::mt19937		  g(rd());
@@ -865,7 +865,7 @@ TEST_CASE("compactcas.compact.totalsize")
 
 			for (int32_t Idx = 0; Idx < kChunkCount; ++Idx)
 			{
-				IoBuffer			   Chunk		= CreateChunk(kChunkSize);
+				IoBuffer			   Chunk		= CreateRandomChunk(kChunkSize);
 				const IoHash		   Hash			= HashBuffer(Chunk);
 				CasStore::InsertResult InsertResult = Cas.InsertChunk(Chunk, Hash);
 				ZEN_ASSERT(InsertResult.New);
@@ -904,7 +904,7 @@ TEST_CASE("compactcas.gc.basic")
 	CasContainerStrategy Cas(Gc);
 	Cas.Initialize(TempDir.Path(), "cb", 65536, 1 << 4, true);
 
-	IoBuffer Chunk	   = CreateChunk(128);
+	IoBuffer Chunk	   = CreateRandomChunk(128);
 	IoHash	 ChunkHash = IoHash::HashBuffer(Chunk);
 
 	const CasStore::InsertResult InsertResult = Cas.InsertChunk(Chunk, ChunkHash);
@@ -923,7 +923,7 @@ TEST_CASE("compactcas.gc.removefile")
 {
 	ScopedTemporaryDirectory TempDir;
 
-	IoBuffer Chunk	   = CreateChunk(128);
+	IoBuffer Chunk	   = CreateRandomChunk(128);
 	IoHash	 ChunkHash = IoHash::HashBuffer(Chunk);
 	{
 		GcManager			 Gc;
@@ -964,7 +964,7 @@ TEST_CASE("compactcas.gc.compact")
 		Chunks.reserve(9);
 		for (uint64_t Size : ChunkSizes)
 		{
-			Chunks.push_back(CreateChunk(Size));
+			Chunks.push_back(CreateRandomChunk(Size));
 		}
 
 		std::vector<IoHash> ChunkHashes;
@@ -1190,7 +1190,7 @@ TEST_CASE("compactcas.gc.deleteblockonopen")
 	Chunks.reserve(20);
 	for (uint64_t Size : ChunkSizes)
 	{
-		Chunks.push_back(CreateChunk(Size));
+		Chunks.push_back(CreateRandomChunk(Size));
 	}
 
 	std::vector<IoHash> ChunkHashes;
@@ -1256,7 +1256,7 @@ TEST_CASE("compactcas.gc.handleopeniobuffer")
 	Chunks.reserve(20);
 	for (const uint64_t& Size : ChunkSizes)
 	{
-		Chunks.push_back(CreateChunk(Size));
+		Chunks.push_back(CreateRandomChunk(Size));
 	}
 
 	std::vector<IoHash> ChunkHashes;
@@ -1308,7 +1308,7 @@ TEST_CASE("compactcas.threadedinsert")
 		{
 			while (true)
 			{
-				IoBuffer Chunk = CreateChunk(kChunkSize);
+				IoBuffer Chunk = CreateRandomChunk(kChunkSize);
 				IoHash	 Hash  = HashBuffer(Chunk);
 				if (Chunks.contains(Hash))
 				{
@@ -1377,7 +1377,7 @@ TEST_CASE("compactcas.threadedinsert")
 
 			for (int32_t Idx = 0; Idx < kChunkCount; ++Idx)
 			{
-				IoBuffer Chunk	= CreateChunk(kChunkSize);
+				IoBuffer Chunk	= CreateRandomChunk(kChunkSize);
 				IoHash	 Hash	= HashBuffer(Chunk);
 				NewChunks[Hash] = Chunk;
 			}
diff --git a/zenstore/filecas.cpp b/zenstore/filecas.cpp
index b4729d558..986cc9ae6 100644
--- a/zenstore/filecas.cpp
+++ b/zenstore/filecas.cpp
@@ -39,7 +39,7 @@ ZEN_THIRD_PARTY_INCLUDES_END
 
 namespace zen {
 
-namespace {
+namespace filecas::impl {
 	const char* IndexExtension = ".uidx";
 	const char* LogExtension   = ".ulog";
 
@@ -77,7 +77,7 @@ namespace {
 
 #pragma pack(pop)
 
-}  // namespace
+}  // namespace filecas::impl
 
 FileCasStrategy::ShardingHelper::ShardingHelper(const std::filesystem::path& RootPath, const IoHash& ChunkHash)
 {
@@ -125,6 +125,8 @@ FileCasStrategy::~FileCasStrategy()
 void
 FileCasStrategy::Initialize(const std::filesystem::path& RootDirectory, bool IsNewStore)
 {
+	using namespace filecas::impl;
+
 	m_IsInitialized = true;
 
 	m_RootDirectory = RootDirectory;
@@ -1013,6 +1015,8 @@ FileCasStrategy::ValidateEntry(const FileCasIndexEntry& Entry, std::string& OutR
 void
 FileCasStrategy::MakeIndexSnapshot()
 {
+	using namespace filecas::impl;
+
 	uint64_t LogCount = m_CasLog.GetLogCount();
 	if (m_LogFlushPosition == LogCount)
 	{
@@ -1062,12 +1066,12 @@ FileCasStrategy::MakeIndexSnapshot()
 
 		BasicFile ObjectIndexFile;
 		ObjectIndexFile.Open(IndexPath, BasicFile::Mode::kTruncate);
-		FileCasIndexHeader Header = {.EntryCount = Entries.size(), .LogPosition = LogCount};
+		filecas::impl::FileCasIndexHeader Header = {.EntryCount = Entries.size(), .LogPosition = LogCount};
 
-		Header.Checksum = FileCasIndexHeader::ComputeChecksum(Header);
+		Header.Checksum = filecas::impl::FileCasIndexHeader::ComputeChecksum(Header);
 
-		ObjectIndexFile.Write(&Header, sizeof(FileCasIndexHeader), 0);
-		ObjectIndexFile.Write(Entries.data(), Entries.size() * sizeof(FileCasIndexEntry), sizeof(FileCasIndexHeader));
+		ObjectIndexFile.Write(&Header, sizeof(filecas::impl::FileCasIndexHeader), 0);
+		ObjectIndexFile.Write(Entries.data(), Entries.size() * sizeof(FileCasIndexEntry), sizeof(filecas::impl::FileCasIndexHeader));
 		ObjectIndexFile.Flush();
 		ObjectIndexFile.Close();
 		EntryCount		   = Entries.size();
@@ -1093,6 +1097,8 @@ FileCasStrategy::MakeIndexSnapshot()
 uint64_t
 FileCasStrategy::ReadIndexFile()
 {
+	using namespace filecas::impl;
+
 	std::vector<FileCasIndexEntry> Entries;
 	std::filesystem::path		   IndexPath = GetIndexPath(m_RootDirectory);
 	if (std::filesystem::is_regular_file(IndexPath))
@@ -1179,6 +1185,8 @@ FileCasStrategy::ReadIndexFile()
 uint64_t
 FileCasStrategy::ReadLog(uint64_t SkipEntryCount)
 {
+	using namespace filecas::impl;
+
 	std::filesystem::path LogPath = GetLogPath(m_RootDirectory);
 	if (std::filesystem::is_regular_file(LogPath))
 	{
@@ -1230,6 +1238,8 @@ FileCasStrategy::ReadLog(uint64_t SkipEntryCount)
 std::vector<FileCasStrategy::FileCasIndexEntry>
 FileCasStrategy::ScanFolderForCasFiles(const std::filesystem::path& RootDir)
 {
+	using namespace filecas::impl;
+
 	std::vector<FileCasIndexEntry> Entries;
 	struct Visitor : public FileSystemTraversal::TreeVisitor
 	{
diff --git a/zenstore/gc.cpp b/zenstore/gc.cpp
index 8d3b8d018..370c3c965 100644
--- a/zenstore/gc.cpp
+++ b/zenstore/gc.cpp
@@ -888,7 +888,7 @@ GcScheduler::CollectGarbage(const GcClock::TimePoint& ExpireTime, bool Delete, b
 
 #if ZEN_WITH_TESTS
 
-namespace {
+namespace gc::impl {
 	static IoBuffer CreateChunk(uint64_t Size)
 	{
 		static std::random_device rd;
@@ -909,10 +909,12 @@ namespace {
 	{
 		return CompressedBuffer::Compress(SharedBuffer::MakeView(Buffer.GetData(), Buffer.GetSize()));
 	}
-}  // namespace
+}  // namespace gc::impl
 
 TEST_CASE("gc.basic")
 {
+	using namespace gc::impl;
+
 	ScopedTemporaryDirectory TempDir;
 
 	CidStoreConfiguration CasConfig;
@@ -940,6 +942,8 @@ TEST_CASE("gc.basic")
 
 TEST_CASE("gc.full")
 {
+	using namespace gc::impl;
+
 	ScopedTemporaryDirectory TempDir;
 
 	CidStoreConfiguration CasConfig;
@@ -1140,6 +1144,8 @@ TEST_CASE("gc.full")
 
 TEST_CASE("gc.diskusagewindow")
 {
+	using namespace gc::impl;
+
 	DiskUsageWindow Stats;
 	Stats.Append({.SampleTime = 0, .DiskUsage = 0});	// 0	0
 	Stats.Append({.SampleTime = 10, .DiskUsage = 10});	// 1	10
diff --git a/zenutil/zenserverprocess.cpp b/zenutil/zenserverprocess.cpp
index 3d9324af9..b43313b7c 100644
--- a/zenutil/zenserverprocess.cpp
+++ b/zenutil/zenserverprocess.cpp
@@ -376,7 +376,7 @@ ZenServerState::ZenServerEntry::AddSponsorProcess(uint32_t PidToAdd)
 
 //////////////////////////////////////////////////////////////////////////
 
-std::atomic<int> TestCounter{0};
+std::atomic<int> ZenServerTestCounter{0};
 
 ZenServerEnvironment::ZenServerEnvironment()
 {
@@ -416,7 +416,7 @@ ZenServerEnvironment::CreateNewTestDir()
 	using namespace std::literals;
 
 	ExtendableWideStringBuilder<256> TestDir;
-	TestDir << "test"sv << int64_t(++TestCounter);
+	TestDir << "test"sv << int64_t(++ZenServerTestCounter);
 
 	std::filesystem::path TestPath = m_TestBaseDir / TestDir.c_str();